dns_compress_rollback
dns_compress_rollback(dns_compress_t *cctx, uint16_t offset);
dns_compress_rollback(msg->cctx,
dns_compress_rollback(msg->cctx, 0);
dns_compress_rollback(cctx, (uint16_t)target->used);
dns_compress_rollback(cctx, (uint16_t)savedbuffer.used);